DP83867IR: Programmable Gain Register

Carsten Rebmann

Part Number: DP83867IR

Tool/software:

Hello support team,

currently there are compliance measurements performed. The product is utilizing the TI DP83867 PHY.

The measurements had been performed, but gets a "FAIL" result with the default settings. But the measurement can be done with "PASS" if using the Programmable Gain Register. Unfortunately, TI records in the Revision History state that this register has been “removed” from the document. And now, of course, there is uncertainty as to whether the setting may be made? And whether it can lead to other problems when using the Programmable Gain Register to increase the signal amplitude…

DP83867IR/CR Robust, High Immunity 10/100/1000 Ethernet Physical Layer Transceiver datasheet (Rev. I)

Best regards

Carsten Rebmann

6 months ago

0 David (ASIC) Liu 6 months ago

TI__Guru**** 176651 points

Carsten

The removal of Reg 0x01D5 Programmable Gain Register (PROG_GAIN) should not affect your design.

The 867IR Version had this register removed because it describes SGMII functionality, where the 867IR does not support SGMII.

What compliance measurement are you seeing the failure?

Thanks

David

0 Carsten Rebmann 6 months ago in reply to David (ASIC) Liu

Prodigy 10 points

The voltage swing is too low and setting the Reg 0x01D5 Programmable Gain Register (PROG_GAIN) enhanced the output drive from the DP83867IR. When this is removed, why does our customer see a enhanced signal when using it?

Thanks
Carsten

0 David (ASIC) Liu 6 months ago in reply to Carsten Rebmann

TI__Guru**** 176651 points

Carsten

Can you also please evaluate the design against our schematic and layout checklists to rule out any board design contributions to the tests?

DP83867IR Reg 0xA0 and 0xA1 can help in adjusting signal amplitude per channel. Please experiment with these fields accordingly to see if they help in these tests. But I would not use Reg 0x01D5 to enhance the output drive strength.

Thanks
David

0 Carsten Rebmann 6 months ago in reply to David (ASIC) Liu

Prodigy 10 points

Hello David,

one more question came up. If we use the DP83867IR Reg 0xA0 and 0xA1 to adjust the signal gain for the compliance testing. How to ensure that the Windows driver in the final product is using the same settings?

Best regards
Carsten

0 David (ASIC) Liu 6 months ago in reply to Carsten Rebmann

TI__Guru**** 176651 points

Carsten

Do they see any actual functional issue with the reduced voltage swing?

Thanks

David

0 Carsten Rebmann 6 months ago in reply to David (ASIC) Liu

Prodigy 10 points

We are in industrial environments. The customer learned in the past that passing compliance tests is very important for interoperability in mixed setups. We are not doing consumer electronics...

Best regards
Carsten

0 David (ASIC) Liu 6 months ago in reply to Carsten Rebmann

TI__Guru**** 176651 points

Carsten

Thanks for the feedback. If you are using the register 0xA0 and 0xA1 to adjust the signal gain, then you do need to modify the Win driver. Unfortunately we do not have much experience with PHY Win driver. Is it possible that you can reach out to Microsoft for support on this one?

The other option is to use a magnetic isolation that has lower insertion loss, this will also help with improving the signal amplitude.

Thanks

David

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DP83867IR: Programmable Gain Register